Electric heating – Heating devices – Tool or instrument
Reexamination Certificate
2001-12-04
2003-10-14
Jeffery, John A. (Department: 3742)
Electric heating
Heating devices
Tool or instrument
C228S051000
Reexamination Certificate
active
06633021
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a soldering iron that is capable of soldering electronic parts, for example with high quality.
2. Discussion of the Related Art
For example in the case where an electronic equipment is assembled, various electronic parts and wires are soldered to an electronic substrate mostly by using a soldering iron. In such a soldering iron, a forward end tip is heated by heating means such as a heater, and this is brought into contact with a land or a workpiece of the electronic substrate so that solder is fused, and the forward end tip is separated so that the solder is solidified. This system is widely adopted.
However, due to a relation that the forward end tip is brought into contact with a soldered portion, a temperature of the forward end tip fluctuates, and thus the temperature of the forward end tip is controlled by voltage control and PDI control. However, the fluctuation of the temperature is vigorous depending on a circumstance of the soldered portions such as a radiation plate, a metal case or an earth terminal or a connector pin which requires extremely large heating value, and thus defective soldering easily occurs.
In addition, a thermal stress due to heat cycle works on the forward end tip, and corrosion of the forward end tip occurs due to diffusion of tin and flux so that a life of the forward end tip becomes short. For this reason, it is necessary to replace the soldering iron with new one every 20,000th to 30,000th time in order to secure the accuracy of the soldering.
On the contrary, Japanese Patent Application Laid-Open No. 07-132369 (1995) suggests a soldering iron where a hot air is discharged onto a periphery of the forward end tip, but facility for generating hot air is required.
In addition, the inventors have developed a soldering iron in such a manner that a heating gas flow generating chamber is formed around heating means for heating a forward end tip and a forward end side of the heating gas flow generating chamber is opened around the forward end tip, and a heating gas flow is generated so as to blowout onto the periphery of the forward end tip (see WO 98/30352).
In the above-mentioned system for blowing out the heating gas flow onto the periphery of the forward end tip, since theoretically the forward end tip is in the atmosphere of the heating gas flow, the fluctuation in temperature of the forward end tip is small, and since a soldered portion can be preheated, this system has an advantage that excellent soldering property can be obtained.
However, In the above structure that the heating gas flow generating chamber is formed around the heating means for heating a forward end tip, the temperature of the heating gas flow is not stabilized, and the above-mentioned effect cannot be occasionally obtained.
SUMMARY OF THE INVENTION
In order to solve the above problem, it is an object of the present invention to provide a soldering iron that is capable of generating a heating gas flow with stable temperature.
Therefore, a soldering iron of the present invention where a forward end tip is heated by heating means contained in a soldering iron main body, whereas a heating gas flow is generated in a heating gas flow generating chamber by heating of the heating means so as to blowout to a periphery of the forward end tip, is characterized in that: a nozzle section is provided to the forward end tip so as to surround its periphery and to be opened forward, whereas an orifice section is formed between the heating gas flow generating chamber and the nozzle section; and a diameter of the orifice section is set to a dimension such that a gas supplied into the heating gas flow generating chamber by constant pressure is heated to be thermally expanded in the heating gas flow generating chamber by heating of the heating means, and a back pressure of the thermally expanded heating gas and a pressure of a gas continuously supplied are balanced in the heating gas flow generating chamber so that a part of the heating gas heated to a predetermined temperature blowouts from the orifice section to the nozzle section, whereas the gas supplied continuously is mixed with the thermally expanded heating gas by a convection so as to be preheated.
One of the features of the present invention is that the orifice section is formed between the heating gas flow generating chamber and the nozzle section, the supplied gas is heated and expanded in the heating gas flow generating chamber, the back pressure and the pressure of the supplied gas are balanced, and a part of the heating gas is allowed to blowout from the orifice section to the nozzle section, whereas the gas successively supplied is mixed with the heating gas by convection so as to be preheated.
As a result, the pressure of the heating gas flow blowout from the orifice section, namely, from the nozzle section is substantially constant as long as the pressure balance is not collapsed, and the temperature is substantially constant, and a temperature of the heating gas flow to be blowout to the periphery of the forward end tip can be controlled in a stable manner.
A number of the orifice section may be one or plural. The form and material quality of the heating means are not particularly limited, but because of the system that the back pressure of the heating gas and the pressure of the supplied gas are balanced, the heating means is a cylindrical heater, and the heating gas flow generating chamber may be formed inside or outside the cylindrical heater.
In addition, a part of the forward end of the forward end tip is utilized for fusing solder, and heated other portions are not utilized usefully. Therefore, in the case where the heating gas flow generating chamber is formed inside the cylindrical heater, it is considered preferable that a backward half portion of the forward end tip surrounds a part of or most part of the heating gas flow generating chamber or is inserted into the heating gas flow generating chamber so that a gas in the heating gas glow generating chamber may be further thermally expanded by radiation of heat stored in the forward end tip.
In addition, a backward half portion of the forward end tip surrounds a part or most part of the heating gas flow generating chamber outside the cylindrical heater so that the gas in the heating gas flow generating chamber can be further thermally expanded by radiation of heat stored in the forward end tip. Particularly in this case, when a metal cylindrical body capable of preventing heat diffusion to the outside is externally fitted to the backward half portion of the forward end tip, heat radiated uselessly from the forward end tip can be recovered and utilized by heating gas so that thermal efficiency can be improved greatly. Namely, also while the soldering work is not carried out, it is conventionally necessary to allow an electric current (stand-by current) to flow in order to maintain the heating means at high temperature, the heat is diffused uselessly, and thus the stand-by current is ineffective as energy. However, as mentioned above when the heat stored in the forward end tip is utilized for heating gas, the ineffective energy can be utilized as effective energy for heating gas. Therefore, the soldering iron of the present invention can execute the soldering work by means of the efficiently heated heating gas flow and the heat of the forward end tip with high energy efficiency. The soldering iron of the present invention is a completely new type soldering iron that can be called as an energy saving type soldering iron or hybrid type soldering iron, and it can contribute to needs in the recent market and global reduction of energy.
The backward half portion of the forward end tip does not surround the heating gas flow generating chamber and the cylindrical heater as mentioned above, but may be inserted into them. Namely, the heating means is the cylindrical heater, the heating gas flow generating chamber is formed outside the cylindrical heater, the backward half portion of the forward
Jeffery John A.
Smith Patent Office
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